64 Injlrufhental TnflruBions 



If you would divide a Circle, fuppofe into 

 fix Parts, the Diameter of the Inftrument be- 

 ing laid on any Line, A C B, and its Center 

 on C, prick ih Hole againft the two Divifi- 

 ons noted 6, on both Sides, and 'tis done. 



The Plain TabUi 



TH I S Inftrument is ufually 15 Indies 

 long, and 12 broad, and is made to fir 

 on three Legs, by a Ball and Socket fitted to a 

 Nofil in the Table. On the jointed Frame on 

 both Sides of it are feveral Lines. On one 

 Side the Line, next the Table, is an Inch-Di- 

 vifion^ the next, a Tangent Line, confitting 

 of 4 Ninety's, centering in the Brafs Hole in 

 the Middle of the Inftrument 5 arid the outer- 

 moft Line is alfo a Tangent Line, divided in- 

 to 360 Parts or Degrees, and each 10 Degrees 

 to go Minutes 5 and has the fame Center as 

 the preceding Line. On the other Side of the 

 jointed Frame, the Divifion next fhe Inftru- 

 jnent, is alfo an Inch-^Divifion, decmially di- 

 vided ^ and the two next are Tangent LineSj 

 confifting of 180 Degrees, and the outermoft 

 of them decimally divided, and each Degree 

 into two thirty's of Minutes. Thefe Lines 

 h^ve for their Center a Brafs Hole, inclining 

 to a Side of the fable ^ and therefore in the 

 Ufeofthem, the Fnme mnft be fo plac'd, 

 that a Line paffing from the Beginning to ^he 



End 



